Suppression lists prevent emails from being sent to specific addresses, helping you honor opt-outs, manage bounces, and protect your sender reputation. There are three types, each under Lists → Suppression:
Email Suppression — block individual addresses. Add them manually, upload a CSV (up to 250MB), or pick a file from the server. Plain-text or MD5-hashed addresses are supported, and a Reference label records why each entry was added.
Domain Suppression — block every address at a domain (competitors, disposable email providers, high-complaint domains). Enter domains without the @ sign.
IP Suppression — when a contact opens or clicks, their IP is checked against this list; on a match the contact is suppressed from future sends. Single IPs, ranges, and CIDR notation are supported.
Each suppression can be Global (blocks across all lists) or list-specific. Contacts are also suppressed automatically by hard bounces and spam complaints, per your bounce rules and feedback loop settings.
Worth knowing: suppression synchronizes every 15 minutes, so new entries may take a sync cycle to fully take effect; IP suppression only applies to contacts who have engaged (opened or clicked); after removing global suppressions, click Re-Sync Suppression to update contact statuses; you can bulk-remove entries that share a Reference label; and before un-suppressing anyone, make sure you have permission to email them again.